Field of the Invention
The present invention relates to a measuring apparatus for measuring the shape of an object.
Description of the Related Art
Along with the recent advances of robot technologies, a robot takes on a complex process such as assembly of an industrial product. To implement assembly by the robot, it is necessary to measure the relative positions and orientations between an end effect such as a hand of the robot and a grip target component. A method of measuring the position and orientation of a target component is described in Japanese Patent No. 5393318. In the method described in Japanese Patent No. 5393318, fitting with a model such as CAD is performed using both edge information obtained from a grayscale image and a range image obtained by a three-dimensional measuring method such as a pattern projection method, thereby measuring the position and orientation of a target component.
To obtain the grayscale image and the range image from a single imaging element, the images need to be obtained by time shift or by separating them from one captured image. To adapt to speedup of the assembly process, the robot needs to measure the position and orientation of the target component while moving. Hence, if the images are obtained by time shift, a positional shift occurs between the images. If the images are obtained by separating them from one captured image, pattern light for the range image is superimposed on the edge of the target component. An edge detection error occurs in the grayscale image, and the measurement accuracy of the position and orientation lowers.
In Japanese Patent No. 5122729, an object is simultaneously illuminated with illumination for a grayscale image and illumination for a range image configured to project pattern light, which have different wavelengths. In the method described in Japanese Patent No. 5122729, light reflected by the object is condensed via an imaging lens and separated into two wavelengths by a wavelength dividing element such as a dichroic prism. After that, a grayscale image and a range image of the same time are obtained using two sensors.
In the method dichroic prism in Japanese Patent No. 5122729, a light beam is separated by the reflecting surface of the dichroic prism, thereby obtaining the range image and the grayscale image. If the reflecting surface is used as in Japanese Patent No. 5122729, the shift of the reflected light beam becomes larger than that of a transmitted light beam when the dichroic prism deforms or changes the position and orientation due to a vibration, a change in the orientation of the apparatus, or a change in the ambient temperature. In particular, when the range image is obtained by the principle of triangulation such as a pattern projection method, a measurement error amount associated with the shift amount of the light beam is amplified depending on the condition of the angle of convergence.